Electric storage air heater

ABSTRACT

A heat storage device for heating rooms comprising a storage core and a fan which conveys air through said core in order to withdraw the heat. The storage core comprises a heat storage material consisting of a hydrate whose liquefaction temperature at solution in its own water of crystallisation comes within the range between approximately 70* and 95*C.

United States Patent Laing et al.

[451 May 20, 1975 ELECTRIC STORAGE AIR HEATER Inventors: Nikolaus Laing; Ingeborg Laing,

both of Hofener Weg 35-37, 7141 Aldingen near Stuttgart, Germany Filed: June 5, 1972 Appl. No.: 260,012

Related US. Application Data Continuation of Ser. No. 13,747, Feb. 24, 1970, abandoned.

US. Cl. 165/961; 165/104; 219/365; 251/11 Int. Cl F28f 27/00 Field of Search 166/96, 104; 219/365; 251/11; 236/68 R, 101 R References Cited UNITED STATES PATENTS 6/1923 Birdsall 165/32 X 2,494,035 l/1959 Christy 219/365 3,048,985 8/1962 Long 236/68 R X 3,131,865 5/1964 Roe 219/365 X FOREIGN PATENTS OR APPLICATIONS 984,096 2/1965 United Kingdom 219/365 1,066,595 4/1967 United Kingdom 219/365 Primary Examiner-Albert W. Davis, Jr.

' Attorney, Agent, or Firm-Pennie & Edmonds [57] ABSTRACT A heat storage device for heating rooms comprising a storage core and a fan which conveys air through said core in order to withdraw the heat. The storage core comprises a heat storage material consisting of a hydrate whose liquefaction temperature at solution in its own water of crystallisation comes within the range between approximately 70 and 95C.

2 Claims, 22 Drawing Figures PATENTEB MAY 2 0 I975 SHEEF 10? 6 PATENTEUHAYZOIBYS WEE-I 2 0F 6 FIG. 5

PATENTEDHAYZOISTS f3. 88 4,295

sum 3 0? a FIG. 8

I LLUU UUUU PATNTEB MAY 20 i975 SHEET 5 BF 6 I ELECTRIC STORAGE AIR HEATER This is a continuation of application Ser. No. 13,747, filed Feb. 24, 1970, now abandoned.

THE PRIOR ART Indirect heat storage by electrical power, steam or hot oil, and transported heat, are becoming increasingly more important.

Stored heat is used, for example, for space heating. Known storage devices for space heating use storage elements which are heated to some hundreds of degrees C, with the result that dust mixed with the room air becomes carbonised at low temperature in said storage elements. This has an adverse effect on the occupants comfort, because of smell for example, and may even have adverse consequences on health.

THE OBJECT OF THE INVENTION The invention therefore relates to a heat storage device in which the air adjacent tothe storage core is heated below the (dust) carbonisation temperature of about 95C when the storage device is being discharged.

DESCRIPTION OF THE INVENTION It has been found that when the heat storage materials used are certain hydrates whose heat of solution on dissolving in, or liquifying in the presence of their own water of crystallisation comes within the range of between about 70 and 95C, that the heat of fusion of the hydrate can be utilised to store and yield up again the heat in the temperature range below the carbonisation temperature. Hydrates that may be used are barium hydroxide octahydrate, ammonia alum dodecahydrate, magnesium hydrate hexahydrate and trisodium phosphate monohydrate. The use of the above hydrates as heat storage materials has the additional advantages that the storage core of heat storage devices according to the invention requires very little external insulation. The insulation, the storage material containers and the casing materials may be made of plastic so that the storage unit casing may have thin walls and may even consist of wood, while a very flat construction is also rendered possible. Thus heat storage devices according to the invention can be used for the production of flat heaters which can be arranged architecturally in interiors and at the optimum' place as regards air conditioning, i.e. beneath windows.

A heat storage device according to the invention also has the great advantage of absolutely excluding any risk of fire and explosions.

Another advantage of using the above lowtemperature storage materials is that chemically inert plastics, e.g. highly cross-linked polythene, which are not of mechanically stable shape at elevated temperatures, but which are at the temperatures now being considered, can be used for the storage material containers. This also solves the problem arising when metal containers are used in known storage devices, which are subjected to inadmissible forces owing to the expansion of the storage materials on melting. The hydrates according to the invention can be used alone or in the form of mixtures with substances which influence the melting point or the discharge temperature/time function.

A preferred heat storage device comprising a storage core containing the above-listed storage materials according to the invention, is constructed as follows:

The storage core comprises a plurality of containers which are filled with heat storage materials and which include between them passages or ducts through which the room air can be conveyed during the discharge period. The storage core can be heated directly or by means of a flowable heat vehicle. The latter is particularly applicable when steam or hot oil are used as heat vehicles. Both of these heat vehicles usually operate at relatively high temperature: steam up to C and hot oil up to 350C, so that the heat losses of the pipes may be very high especially if the pipes carrying the heat vehicle carry the heat vehicle during 24 hours. In conjunction with heat storage devices according to the invention, charging can be limited, for example, to two or three periods each of one hour distributed throughout the day, so that the heat losses are reduced to about shown in FIG. 1a, with various valve positions, the side wall of the housing of the device having been omitted.

FIG. 2 is a perspective view of an embodiment of a storage element for the heat storage device shown in FIG. 1a to 10.

FIGS. 3 to 7 are partly perspective views and partly sectional views of various embodiments and possible associations of storage elements for a heat storage device according to the invention.

FIG. 8a is a broken plan view of a plate-shaped heater element for a heat storage device according to the invention.

FIG. 8b is a side sectional view of FIG. 8a.

FIG. 9 is a diagrammatic elevation of a plate-shaped heating register for a heat storage device according to the invention.

FIG. 10 is a partial perspective and partial section of one embodiment of a storage core for a heat storage device according to the invention, with heating elements in the form of resistance-heating wires.

FIG. 11 is a partial perspective and partial section of a roller type closure for the air duct of a storage device according to the invention.

FIG. 12a is a partial vertical section and partial perspective-of another embodiment of a storage device according to the invention.

FIG. 12b is a front elevation of the storage device shown in FIG. 12a, the front plate having been removed.

FIG. 13 is a section on the line aa in FIG. 12a showing the storage core of the device shown in FIG. 12a. 1

FIG. 14 is another embodiment of a closure flap for an air duct of a storage device according to the invention.

FIG. 15a is an elevation of another embodiment of a storage device according to the invention having an injector disposed at the bottom.

- FIGS. 15b and 15c are sections on the lines b-b and cc in FIG. 15a.

FIG. 16a is a front elevation of a similar device to FIG. 15a.

FIG. 16b is a section on the line bb in FIG. 16a.

FIG. 1a shows a storage device according to the invention comprising an air inlet grid 1 and an air outlet grid 2. As indicated by the lines 3, the width of the device can be selected to any desired size in units of dimension corresponding with the storage elements which are constructed as modules. Since in practice little or no insulation is necessary the device can be made very flat and, unlike some known devices, can be suspended at a very small distance from the wall.

As will be apparent from FIGS. 11; and 1c, the three storage elements 5 are so disposed that they form two air ducts 6 and 7 extending over the entire width of the device and which communicate with one another at the top and bottom. In FIG. 1b, a butterfly valve 8 is shown in a position in which air can flow in the direction of the arrow 9 through the ducts 6, 7, of the device. In the position of the valve 8 shown in FIG. 1c, the air outlet to the room through the grid 2 is blocked and the air can circulate in a closed circuit in the direction of the arrows 11 and 12, the heating element 13, formed like a guide blade, heating and guiding the air flow.

"FIG. 2 shows a storage element whose storage material container consists of two identical L-sectioned members 21 and 22 and end walls 23. A filling connection 24 is provided in one of the end walls 23. Heat exchange surfaces 25 like fins are secured to the container on one or both sides, depending upon whether the storage element is disposed in the middle or on the outside of the storage core in the manner of FIGS. 1b and 1c. The containers may consist of sheet metal but are preferably made from plastic.

FIG. 3 shows four storage material container units made of plastic, in which in order to simplify stacking, filler connections 32 are disposed at bevelled corners 31. Heat conducting surfaces 33 of metal are stuck to the individual containers or else they are fitted, on assembly, in the form of resilient firmly-contacting intermediate members having a length corresponding to the total usable width of the device.

FIG. 4 is a perspective and a horizontal section illustration through a heat storage device according to the invention. The storage elements are supported on a frame (not shown) which has apertures equal to the width of the rectangular zig-zag conductive fins 40. The storage elements are constituted by means of rectangular-sectional tubular sheet metal casings 41. The storage material in each container is accommodated in additional containers 42 and 43 comprising plastic sheeting. Between the sheet-metal casing and the containers 42 and 43 a flat heater 44 is provided and will be explained in detail with referenceto FIG. 8. The storage material which is introduced in the flowable state presses the walls of the plastic containers 42 and 43 tightly against the heater 44.

In the embodiment illustrated in FIG. 5, the storage material containers consist of rectangular-sectional rugated sheet-metal strips 61 which are spaced apart to form the air duct 63. The groups of storage elements situated opposite the metal strips 61 forming the air ducts are in contact with a flat heater 62 which also corresponds to the flat heater described with reference to FIG. 9.

The corrugated sheet-metal strips 61 preferably consist of aluminium and during charging and discharging conduct heat to and away from the storage elements.

The heat-exchanging surface area is preferably enlarged by corrugation as illustrated. When the heating is switched on and the valve 8 is open to the exit 2, cooling is so intensive that the melting point of the storage material is not reached, so that all the heat is discharged via the sheet-metal strips 61 to the passing air for immediate (non-storage) heating purposes.

FIG. 7 shows a storage device according to the invention wherein the storage material is disposed in elongated foil tubes 80. The tubes are suspended from rods 81 and are so spaced apart that they present but little resistance to the air rising between them. The control flap 82 for discharging and charging is hinged at 83. In the changing condition the flap 82 closes the top of the casing in which the storage elements are housed. The bottom 84 of the casing forms a channel-shaped recess 85 so that in the event of any of the containers 80 leaking, none of the storage material can escape. The individual containers 80 enclose resistance heating coils 86 consisting of very thin resistance wire or a conductive polymer. These coils 86 are used primarily to heat the storage element, while secondarily they may increase the mechanical strength of the walls of the storage elements 80 in respect of bursting stress. Instead of the coils 86, thin metal sheets may be used, to act as heating resistances and contribute to mechanical strength.

FIG. 8a and FIG. 8b illustrate in a broken plan and side sectional views a heater for a device according to the invention. The heater comprises a plastic sheeting or foil foundation 100, on which heating conductors have been deposited. The supply lead 101 feeds the resistance circuits 102, 103 and 104 which can each be switched on independently of one another so that recharging is possible without overheating already melted or recrystallized storage material. The plastic sheeting or foil bearing the heating conductor is enclosed in an insulating foil 106 which is welded along the seam 107.

FIG. 9 shows a heating element constructed in the same way and wherein the heating elements, divided into two circuits 110 and 111 for charging purposes, are provided on one side of the heating conductor carrier, while the other side of the carrier bears the heating conductor coating 1 12 which is used for supplementary heating. The latter, by means of which the air can be heated directly, is situated in the region of the air ducts and cannot therefore deliver heat to the storage material, but only to the air passing through the air duct.

In the embodiment shown in FIG. 10, a storage material container is provided with vertical air ducts 121 within which are supported radiation heating elements 122 which in the simpled case are constructed as flat wires suspended between resilient bowed member 123 and 124. When the air flow is interrupted these wires are used for charging purposes by yielding their heat by radiation to the surrounding storage elements, while when the air ducts are open most of the heat of the wires is yielded by direct exchange to'the airflowing through the ducts 121 so that the same heating elements are usable both for storage and for direct air convection heating.

FIG. 11 illustrates a further embodiment wherein the top part of an air ventilation duct can be opened or closed by means of a roll 140. Hinge mounted flaps conventionally used for closing ventilation passages or ducts have a disadvantage in that when the flap is nearly closed, a region of low pressure is created in the gap between the flap and the duct due to the velocity of the moving air. This region of low pressure causes the flap to close completely after which it will then reopen due to the static pressure in the duct acting on the flaps. The result is that the flap will continually open and shut causing an undesirable chattering sound. Further, hinge mounted flaps require sensitive mechanical support means for the pivot axis of the flap further adding to the cost of the structure.

An advantage of using a role type flat as shown in FIG. 11 is that, among other things,-the use of an expensive hinge type structure is eliminated and the tendency of chattering is reduced. As illustrated, the roll 140 comprises two laminae having different coefficients of thermal expansion where the roll is connected at one end to a heat storage member 141 and to an electrical circuit. One lamina may be made of a conductive polymer with the other lamina being nonconductive or the two laminae may comprise a very thin bimetallic strip. The construction of the roll is such that when the circuit is energized, the two laminae orbimetallic strips will become heated. Because of the difference in coefficient expansion, the roll will tend to unroll and close the duct 142. The installation could of course be reversed so that when the current is switched on the roll is rolled up and frees the flow through duct 142 while the duct is closed when the current is switched off.

Examples of lamina material used to form the individual lamina are phenolic resin, polyamide, polytetrafluorethylene, polytrifluorochlorethylene and polyvinyl chloride. As the co-efficient of thermal expansion of each of the materials is different, any two lamina when sandwiched together and where each lamina is made from one of the materials will form a laminate which will roll or curl when subjected to a temperature change. Any of the lamina from the above materials may be made electrically conductive by coating the lamina with carbon.

FIG. 12a, 12b and 13 show another embodiment of a storage device according to the invention wherein the storage materials are contained in plastics containers 150 and 151. Two identical sinuously-shaped heat exchange elements 152 and 153 are disposed between the containers 150/15] and are offset in relation to one another as illustrated. The surface heating element 154 corresponds to the heating element shown in FIG. 8.

nozzles 158 lead into a diffuser 157. The air emerging from the nozzles 158 draws in secondary air. The entire air flow passes through the device. When the air delivery is started, the foil strip 159 opens by reason of becoming hot, said strip being rigidly anchored at one edge. As will be seen in FIG. 12b, a fan 160 is connected to the air duct 155. The storage material containers are so dimensioned that they can be readily transported in the form of boxes.

FIG. 13 is a section on the line a-a in FIG. 12a, showing the arrangement of the nozzles 156 and elements 152 and 153. The heating element 154 is disposed between elements 152 and 163.

FIG. 14 shows the construction of the flap 159 of the device according to FIG. 12a, which is suspended in eyelet-like hinges and is opened by the pressure of the incoming air.

FIGS. 15a to 156 show another embodiment of a device according to the invention, comprising two identical halves and 191, and an air shaft 192 at the feet of which is a fan 193. As will be clear from the sectional views in FIGS. 15b and 150, the storage elements 194 and 195 enclose the heat-exchanger plates 196 between them. Beneath the device is an air space which diverges towards the wall 197 of the room and comprises two ducts 198 and 199. These two ducts communicate with a plurality of profiled tubes 200 which have nozzles 201 extending towards the air shaft 198. Air passes through these nozzles 201 from the ducts 198 and 199 into the duct 202 and draws in secondary air through the intermediate spaces 203 between adjacent tubes 200. The fan 193 maintains the pressure in the 1 ducts 1.98 and 199 and supplies primary air to said ducts. i

In the embodiments shown in FIGS. 16a and 16b, which again comprises two identical halves 207, the fan 208 is disposed at the back of the storage device and draws in air through the entry grid 209 and the shaft 210.

What we claim is:

l. A heat storage device having an air duct therein and a closure for said duct, said closure comprising a flexible composite laminated strip member normally wound in a roll form arid made up of at least two laminae of polymeric material having different coefficients of thermal expansion, said strip being secured at one end thereof adjacent said air duct, an electrical resistance heating means associated with one of said lamina whereby said one lamina may be heated to cause said one lamina to expand relative to said other lamina and to unwind said strip to mask said air duct in order to regulate passage of air therethrough.

2. A heat storage device according to claim 1 whereby said one lamina having the heating means associated therewith comprises an electrically conductive polymeric material. 

1. A heat storage device having an air duct therein and a closure for said duct, said closure comprising a flexible composite laminated strip member normally wound in a roll form and made up of at least two laminae of polymeric material having different coefficients of thermal expansion, said strip being secured at one end thereof adjacent said air duct, an electrical resistance heating means associated with one of said lamina whereby said one lamina may bE heated to cause said one lamina to expand relative to said other lamina and to unwind said strip to mask said air duct in order to regulate passage of air therethrough.
 2. A heat storage device according to claim 1 whereby said one lamina having the heating means associated therewith comprises an electrically conductive polymeric material. 